1. Technical Field
The present invention relates to the field of diagnostic ultrasound, and more particularly, to a method of estimating surface temperature of an ultrasound probe used in diagnostic ultrasound imaging.
2. Background Art
The ultrasound imaging diagnostic system has become an important and popular diagnostic tool due to its non-invasive and non-destructive nature. Modern high-performance ultrasound imaging diagnostic systems and techniques are commonly used to produce two- or three-dimensional images of internal features of patients.
A diagnostic ultrasound system generally uses a probe containing an array of piezoelectric elements to transmit and receive ultrasound signals. The ultrasound imaging diagnostic system forms an image of human internal tissues by electrically exciting transducer elements to generate ultrasound signals that travel into the body. Echoes reflected from tissues and organs return to the transducer element and are converted into electrical signals, which are amplified and processed to produce a diagnostic image.
FIG. 1 is a schematic diagram showing the structure of an ultrasound probe. As shown in FIG. 1, ultrasound probe 100 includes an array of transducer elements 110, matching layer 120, acoustic lens 130, and backing layer 140. Transducer elements 110 are made of a piezoelectric material, such as lead zironate titanate (PZT) and convert an electric input to an ultrasound signal and vice versa. Matching layer 120 may be formed with a plurality of layers and is used to reduce the reflection of the ultrasound signal, due to acoustic impedance mismatch between transducer elements 110 and human body. Lens 130 is to focus the ultrasound signals, while backing layer 140 is used for damping out vibration of the transducer elements to generate a short well defined ultrasound pulse.
When an electrical input is applied to transducer elements 110, some of the electrical energy is converted to heat, leading to a rise in probe surface temperature. For the purpose of patient safety and regulatory compliance, surface temperature rise due to probe self-heating must be accurately predicted and controlled in real time, because, otherwise, it may cause harm to a patient having an ultrasound exam.
Because of the complicated internal geometry of a diagnostic ultrasound probe and the lack of accurate material data, it is difficult to analyze and predict heat generation and the resulting surface temperature rise. Therefore, estimation of probe surface temperature is often based on empirical methods. Empirical methods, however, are expensive and time-consuming because they require large numbers of measurements under various possible operation conditions, e.g., imaging modes, input voltages, penetration depths, and etc. Also, empirical methods sometimes yield inaccurate predictions for operation conditions that are not covered by measurements.
Thus, the present invention overcomes the above-noted deficiencies in the art.